Stress relieved rectilinear duct

ABSTRACT

A duct liner includes a corner flanked by a pair of keyhole slots. An exhaust duct assembly includes an impingement liner received within a duct and a duct liner received within the impingement liner, the duct liner with a multiple of corners, each of the corners flanked by a pair of keyhole slots.

This application claims priority to U.S. Patent Appln. No. 61/765,208filed Feb. 15, 2013.

BACKGROUND

The present disclosure relates to a duct and, more particularly, to arectilinear duct with stress relief.

Gas turbine engines, such as those which power modern military aircraft,include a compressor section to pressurize a supply of air, a combustorsection to burn a hydrocarbon fuel in the presence of the pressurizedair, and a turbine section to extract energy from the resultantcombustion gases and generate thrust. An augmentor section, or“afterburner”, may be located downstream of the turbine section toselectively increase thrust.

In some buried engine arrangements, an exhaust duct downstream of theaugmentor may be at least partially rectilinear in cross-section Arectangular shaped duct exposed to hot gases may result in relativelyhigh corner stresses.

SUMMARY

A duct liner according to one disclosed non-limiting embodiment of thepresent disclosure includes a corner flanked by a pair of keyhole slots.

A further embodiment of the present disclosure includes, wherein each ofthe pair of keyhole slots are displaced from the corner.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the pair of keyhole slots extendparallel to the corner.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the pair of keyhole slots extendthrough a flange

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the pair of keyhole slots arelinear.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the pair of keyhole slots includesa circular end.

An exhaust duct assembly according to another disclosed non-limitingembodiment of the present disclosure includes an impingement linerreceived within the duct; and a duct liner received within theimpingement liner, the duct liner with a multiple of corners, each ofthe corners flanked by a pair of keyhole slots.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the pair of keyhole slots aredisplaced from the corner.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the pair of keyhole slots extendparallel to the corner.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of the pair of keyhole slots extendthrough a duct liner flange of the duct liner.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein the duct liner flange abuts an impingementliner flange of the impingement liner.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes a gasket between the duct liner flange and theimpingement liner flange.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein the duct liner flange abuts a bulkhead.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein the bulkhead is defined by a gas turbineengine.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein the bulkhead is defined by a Hot AcousticRig.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein each of said pair of keyhole slots includesa circular end.

A further embodiment of any of the foregoing embodiments of the presentdisclosure includes, wherein said circular end is displaced from eachcorner by 2.5 times a diameter of said circular end.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation of the inventionwill become more apparent in light of the following description and theaccompanying drawings. It should be understood, however, the followingdescription and drawings are intended to be exemplary in nature andnon-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art fromthe following detailed description of the disclosed non-limitingembodiment. The drawings that accompany the detailed description can bebriefly described as follows:

FIG. 1 is a general schematic view of an exemplary gas turbine enginewith an exhaust duct section according to one disclosed non-limitingembodiment;

FIG. 2 is a general perspective view of the exhaust duct sectionaccording to one disclosed non-limiting embodiment;

FIG. 3 is a general schematic view of an exemplary Hot Acoustic Rig withan exhaust duct section according to another disclosed non-limitingembodiment;

FIG. 4 is an exploded perspective view of an exhaust duct assembly;

FIG. 5 is an expanded view of a duct liner corner; and

FIG. 6 is a schematic view of a duct liner corner illustrating only onekeyhole slot.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool low-bypassaugmented turbofan that generally incorporates a fan section 22, acompressor section 24, a combustor section 26, a turbine section 28, anaugmenter section 30, an exhaust duct section 32, and a nozzle system 34along a central longitudinal engine axis A. Although depicted as anaugmented low bypass turbofan in the disclosed non-limiting embodiment,it should be understood that the concepts described herein areapplicable to other gas turbine engines including non-augmented engines,geared architecture engines, direct drive turbofans, turbojet,turboshaft, multi-stream variable cycle and other engine architectureswith a nozzle system.

The exhaust duct section 32 may be generally rectilinear incross-section (also shown in FIG. 2). It should be appreciated that theexhaust duct section 32 may be mounted to the gas turbine engine 20 orbe mounted to other systems such as a propane burner 50 operable as partof a Hot Acoustic Rig 52 (FIG. 3) to heat components for hightemperature testing. That is, the exhaust duct section 32 may beutilized in numerous ways and be of various rectilinear shapes.

With reference to FIG. 4, the generally rectilinear exhaust duct section32 includes an exhaust duct assembly 60. The exhaust duct assembly 60generally includes a duct liner 62, a gasket 64, an impingement liner 66and a duct 68. The impingement liner 66 is mounted within the duct 68 tointerface with a multiple of bumpers 70 that provide resilient support.The duct liner 62 is mounted within the impingement liner 66 tointerface with a multiple of bumpers 72. Fasteners 74 are mountedthrough a duct flange 76, and an impingement liner flange 78 such that aduct liner flange 80 is sandwiched between a bulkhead 82 (illustratedschematically) and the impingement liner flange 78 with the gasket 64therebetween. The bulkhead 82 is representative of, for example, theengine 20, the rig 52 or other upstream system or systems.

With reference to FIG. 5, the duct liner 62 is generally rectilinear andincludes a multiple of corners 84. A keyhole slot 86 flanks each corner84. Each keyhole slot 86 generally includes a linear slot 88 with adistal end 90 that may be circular in shape. The pairs of keyhole slots86 are parallel to and near each corner 84 to minimize the accumulationof thermal strain by allowing the duct liner flange 80 to deform as theduct liner flange 80 is cooler than the duct and resists the thermalexpansion of the duct 68. Each keyhole slot 86 is approximately 1.15inches (30 mm) in length and displaced from each corner 84 byapproximately 2.5 time the diameter of the of distal ends 90 (FIG. 6).That is, for a distal end of 0.2 inches (5 mm) in diameter, each keyholeslot 86 is displaced approximately 0.5 inches (12.5 mm) from the corner84.

The pairs of keyhole slots 86 minimize the accumulation of thermalstrain through controlled deformation as the duct liner flange 80 cannototherwise carry a bending load at the corners 84. That is, the pairs ofkeyhole slots 86 which flank each corner 84 permit controlled moment tominimize the accumulation of thermal strain.

It should be understood that like reference numerals identifycorresponding or similar elements throughout the several drawings. Itshould also be understood that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom.

Although the different non-limiting embodiments have specificillustrated components, the embodiments of this invention are notlimited to those particular combinations.

It is possible to use some of the components or features from any of thenon-limiting embodiments in combination with features or components fromany of the other non-limiting embodiments.

Although particular step sequences are shown, described, and claimed, itshould be understood that steps may be performed in any order, separatedor combined unless otherwise indicated and will still benefit from thepresent disclosure.

The foregoing description is exemplary rather than defined by thelimitations within. Various non-limiting embodiments are disclosedherein, however, one of ordinary skill in the art would recognize thatvarious modifications and variations in light of the above teachingswill fall within the scope of the appended claims. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced other than as specifically described. For that reasonthe appended claims should be studied to determine true scope andcontent.

What is claimed is:
 1. A duct liner comprising: a corner flanked by apair of keyhole slots.
 2. The duct liner as recited in claim 1, whereineach of said pair of keyhole slots are displaced from said corner. 3.The duct liner as recited in claim 1, wherein each of said pair ofkeyhole slots extend parallel to said corner.
 4. The duct liner asrecited in claim 1, wherein each of said pair of keyhole slots extendthrough a flange.
 5. The duct liner as recited in claim 1, wherein eachof said pair of keyhole slots are linear.
 6. The duct liner as recitedin claim 5, wherein each of said pair of keyhole slots includes acircular end.
 7. An exhaust duct assembly comprising: a duct; animpingement liner received within said duct; and a duct liner receivedwithin said impingement liner, said duct liner with a multiple ofcorners, each of said corners flanked by a pair of keyhole slots.
 8. Theassembly as recited in claim 7, wherein each of said pair of keyholeslots are displaced from said corner.
 9. The assembly as recited inclaim 7, wherein each of said pair of keyhole slots extend parallel tosaid corner.
 10. The assembly as recited in claim 7, wherein each ofsaid pair of keyhole slots extend through a duct liner flange of saidduct liner.
 11. The assembly as recited in claim 10, wherein said ductliner flange abuts an impingement liner flange of said impingementliner.
 12. The assembly as recited in claim 11, further comprising agasket between said duct liner flange and said impingement liner flange.13. The assembly as recited in claim 12, wherein said duct liner flangeabuts a bulkhead.
 14. The assembly as recited in claim 13, wherein saidbulkhead is defined by a gas turbine engine.
 15. The assembly as recitedin claim 13, wherein said bulkhead is defined by a Hot Acoustic Rig. 16.The assembly as recited in claim 7, wherein each of said pair of keyholeslots includes a circular end.
 17. The assembly as recited in claim 16,wherein said circular end is displaced from each corner by 2.5 times adiameter of said circular end.